These days, the Super Bowl is less about pigskin than it is about greenbacks. Television networks cough up billions of dollars to air it, then charge companies marketing beer, babes and tax-preparation software $4 million for just 30 seconds of screen time during it. NFL coaches can score bonuses worth as much as half a million for winning it, and athletes earn an extra $44,000 just for playing in it.

But there’s one entity in this vast entertainment extravaganza that won’t be making a dime from the NFL on Super Bowl Sunday: Beyoncé, the halftime performer.

From the time of the Super Bowl I halftime show, when the University of Arizona and the University of Michigan marching bands performed, the NFL has not paid performers an appearance fee. This tradition has been maintained even though the marching-band shows of the 1960s and ’70s have since been replaced by world-famous acts like the Rolling Stones, the Who and now Beyoncé.

Why would artists donate time and energy to help a television network keep the football audience in front of their TVs for several extra rounds of high-priced commercials? According to Who front man Roger Daltrey, the Super Bowl is an opportunity for increased exposure, even for a band that’s already sold 100 million records. “You can be touring like we have for 50 years, and there’s billions of people who have still never heard of you,” Daltrey says. “That’s the nature of the media these days.”

When the Who performed at Super Bowl XLIV in 2010, they played for an audience of 106 million television viewers in the U.S. in addition to the 74,000 people at the Sun Life Stadium in Miami. Last year Madonna’s halftime show actually garnered more viewers than the game itself, making it the most watched event in television history. From the NFL’s perspective, such publicity is payment enough.

“We’re putting someone up there for 12 and a half minutes in front of the largest audience that any television program garners in the United States,” says Lawrence Randall, director of programming for the NFL. “It’s a pretty good deal. It’s the famous win-win for both parties.”

Indeed, the Who did win on the charts. Digital purchases of the band’s music quadrupled the week after its Super Bowl performance, according to Nielsen, and physical albums also saw a large spike in sales. When the Black Eyed Peas performed in 2011, their digital sales jumped from 196,000 tracks pre–Super Bowl to 406,000 the next week. Madonna’s catalog performed similarly last year. Predictably, the songs actually sung during halftime received the biggest boost.

In addition to the boost to the bottom line, performing at the Super Bowl acts as a type of affirmation of an artist’s pop-culture ubiquity. In recent years, the halftime show has shifted away from gathering an ensemble of current artists and instead centers on one blockbuster act. “Your grandma watches it, your parents watch it, your cousins, no matter what age they are,” Randall says. “We’re looking to entertain the largest group of people we possibly can.”

Though the artist isn’t getting paid, the halftime show is still an expensive affair. The NFL pays for the staging and production of the event, which a league official confirmed cost millions of dollars. PepsiCo is serving as the halftime show’s sponsor this year, organizing a crowdsourced halftime-show introduction that has received more than 100,000 fan submissions. Though Pepsi declined to disclose the terms of its deal with the NFL, the league’s previous halftime sponsorship deal with Bridgestone Tires was worth an estimated $10 million over three years.

While the artists get boosted exposure and record sales, the NFL — and more critically, advertisers — gets an assurance that fans won’t change the channel while players hit the locker room. Back in 1992, while the halftime show on CBS honored the Winter Olympics, Fox aired a special live episode of their hit sketch comedy show In Living Color during the time slot. The episode pulled in 22 million viewers and sent Super Bowl viewership tumbling 22%. The next year, the NFL booked Michael Jackson for halftime — yes, for free — and the event has been a spectacle ever since.

Months of planning lead up to the 12 minutes of entertainment that are now a tentpole of American pop culture. Approximately 500 volunteers, typically residents of the game’s host city, are responsible for building and then breaking down the stage in a matter of minutes. “It’s quite a difficult spot to do,” Daltrey says. “People really, really sweat to get that thing right, and not just the artist. There’s hundreds of people behind them. It’s like an army on the move.”

Daltrey says the Who, who did a medley of hits like “Pinball Wizard” and “Won’t Get Fooled Again,” recorded a version of their performance prior to the game but also played the songs live on the field. The telecast alternated between the two versions. “You want to do as good as you can, but you’re never in charge of those events,” he says. “Sometimes they don’t use what you’re singing. They have to do this process to cover themselves because if they get a technical glitch, you’re going to have 12 minutes of someone you’re not going to hear at all.” An NFL official declined to clarify whether use of a backing track is typical for Super Bowl performances.

The show, which had cycled through a number of older acts following Janet Jackson’s “wardrobe malfunction” in 2004, has been inching toward contemporary acts in recent years, with artists like the Black Eyed Peas, M.I.A. and Usher taking the stage. Such artists may stand to gain even more financially from a Super Bowl gig as digital sales come to dominate the music market. The boost in digital sales has consistently increased over the past three years, likely because viewers can act on an impulse to buy an artist’s music without even leaving the couch. “While the game is playing or after the game is done, you see those boosts start to pick up,” says Dave Bakula, senior vice president for client insights at Nielsen. “This is instantaneous.”

The halftime show has essentially become “a five-song commercial,” Bakula says. Like the commercials, Beyoncé’s performance will likely be heavily dissected in the coming week, and she’ll be compared with previous acts like Madonna and the Who.

However it turns out, Daltrey says the spectacle itself is worthy of admiration. “It’s a challenge for everybody. We take it so for granted,” he says. “Every artist on that stage has got an enormous pair of balls just to do it in the first place.”